Mozharness now lives in Gecko

What's changed?

continuous-integration and release jobs that use Mozharness will now get Mozharness from the Gecko repo that the job is running against.

How?

Whether the job is a build (requires a full gecko checkout) or a test (only requires a Firefox/Fennec/Thunderbird/B2G binary), automation will first grab a copy of Mozharness from the gecko tree, even before checking out the rest of the tree. Effectively minimizing changes to our current infra.

This is thanks to a new relengapi endpoint, Archiver, and hg.mozilla.org's sub directory archiving abilities. Essentially Archiver will get a tar ball of Mozharness from within a target gecko repo, rev, and sub-repo-directory and upload it to Amazon's S3.

What's nice about Achiver is that it is not restricted to just grabbing Mozharness. You could, for example, put https://hg.mozilla.org/build-tools in the Gecko tree or, improving on our tests.zip model, simply grab subdirectories from within the testing/* part of the tree and request them on a suite by suite basis.

What does this mean for you?

it depends. if you are...

1) developing on Mozharness

You will need to checkout gecko and patches will now land like any other gecko patch: 1) land on a development tree-branch (e.g. mozilla-inbound) 2) ride the trains. This now means:

we can have tree specific configs and even scripts

the Mozharness pinning abstraction layer is no longer needed

we have more deterministic builds and tests as the jobs are tied to a specific Gecko repo + rev

there is more transparency on how automation runs continuous integration jobs

there should be considerably less strain on hg.mozilla.org as we no longer rm + clone mozharness jobs

development tree-branches (inbound, fx-team, etc) will behave like the Mozharness default branch while mozilla-central will act as production branch.

This also means:

Mozharness patches that require tree wide changes will need to be uplifted across trees

development on Mozharness will require a Gecko tree checkout

Github + Travis tests will not be run on each Mozharness change (mh tests will have to be run locally for now)

Mozharness changes will not be documented or visible (outside of diffing gecko revs)

2) just needing to deploy Mozharness or get a copy of it without gecko

Like the usage docs linked to Archiver above, you could hit the API directly. But I recommend using the client that buildbot uses. The client will wait until the api call is complete, download the archive from a response location, and unpack it to a specified destination.

Let's take a look at that in action: say you want to download and unpack a copy of mozharness based on mozilla-beta at 93c0c5e4ec30 to some destination.

Note: if that was the first time Archiver was polled for that repo + rev, it might take a few seconds as it has to download Mozharness from hgmo and then upload it to S3. Subsequent calls will happen near instantly

Note 2: if your --destination path already exists with a copy of Mozharness or something else, the client won't rm that path, it will merge (just like unpacking a tarball behaves)

3) a Release Engineering service that is still using hg.mozilla.org/build/mozharness

Not all Mozharness scripts are used for continuous integration / release jobs. There are a number of Releng services that are based on Mozharness: e.g. Bumper, vcs-sync, and merge_day. As these services transition to using Archiver, they will continue to use hgmo/build/mozharness as the Repository of Record (RoR).

If certain services that can not use gecko based Mozharness, then we can fork Mozharness and setup a separate repo. That will of course mean such services won't receive upstream changes from the gecko copy so we should avoid this if possible.

If you are an owner or major contributor to any of these releng services, we should meet and talk about such a transition. Archiver and its client should make deployments pretty painless in most cases.

Have something that may benefit from Archiver?

If you want to move something into a larger repository or be able to pull something out of such a repository for lightweight deployments, feel free to chat to me about Archiver and Relengapi.